Gas burners

ABSTRACT

A gas burner comprising a gas supply element having an outlet, and a gas deflector disposed adjacent the outlet, the position of the deflector, relative to the outlet, being adjustable so as to allow the extent of deflector-induced aeration to be altered.

FIELD OF THE INVENTION

The present invention relates to gas burners, and particularly, but byno means exclusively, to so-called neat gas burners, in which no or aminimal amount of air is mixed with the feed gas upstream of the area ofcombustion. Such burners find application, for example, in commercialcooking appliances such as fryers.

BACKGROUND TO THE INVENTION AND OVERVIEW OF THE PRIOR ART

Gas burners are well-known and are used in a wide variety ofapplications. A typical gas burner may include a burner bar in, the formof a conduit having a gas inlet and one or more openings along itslength to provide gas outlets through which the gas is emitted, prior tocombustion. The gas is emitted in the form of jets, which are ignited toproduce heat. For most domestic applications, natural gas (a “secondfamily” gas) is used as the fuel, although “third family” gases such asliquid petroleum gas (LPG), butane and propane may also be used. Usingthese types of gas can require that a large amount of air be availableto ensure complete combustion, and this has led to the use of a“pre-aeration” stage in conventional gas burners, typically comprising ashort tube in which the air and gas are mixed before the mixture isemitted through the gas outlets. Although this pre-aeration stage helpsto achieve complete combustion of the gas, it adds to the cost andcomplexity of manufacturing gas burners.

In an attempt to overcome this problem, the technology of neat gasburners has been used. In such burners, no pre-aeration chamber orprocess are used, upstream of the area of combustion, and thus neat gasburners can be cheaper and simpler to manufacture.

This type of burner was originally developed to burn “first family” towngas, which is derived from coal, and which does not require as much airas second and third family gases for complete combustion. In adaptingthis type of burner to use second and third family gases, it was foundthat there was insufficient air present for complete combustion tooccur. To alleviate this, neat gas burners for second and third familygases have tended to include a baffle near the gas outlets such that gasescaping from the outlets is deflected by the baffle, resulting inturbulence, which causes the gas to mix with the surrounding air. Themixture of gas and air is ignited at the point where the gas hits thebaffle, resulting in combustion of the gas.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda gas burner comprising a gas supply element having an outlet, and a gasdeflector disposed adjacent the outlet; the position of the deflector,relative to the outlet, being adjustable so as to allow the extent ofdeflector-induced aeration to be altered.

The angle of the deflector; relative to the outlet, may be adjustable.

The spacing of the deflector, relative to the outlet, may be adjustable.

Preferably both the angle and spacing of the deflector, relative to theoutlet, are adjustable.

The supply element may comprise a conduit having a plurality of spacedoutlets, the deflector being provided by a baffle surface adjacent theoutlets, such that gas emitted therefrom is incident upon spaced regionsof the baffle surface.

The conduit may be a closed pipe, conveniently being generally straight,with the baffle surface extending generally parallel thereto.

Preferably, the baffle surface is generally flat.

The baffle surface may be inclined relative to the gas streams emittedthrough the outlets.

The baffle surface may have a distal ridge, with the distance of thedistal ridge from the gas steams desirably being adjustable.

The gas burner may further comprise an air guide to assist in theentrainment of air with gas emitted from the outlet.

The air guide may have guide surfaces disposed on at least two sides ofthe outlet.

The outlet may be generally horizontally-disposed, with the guidesurfaces being disposed above and below the outlet.

According to a second aspect of the invention, there is provided a gasburner comprising a gas supply element having an outlet for the emissionof a gas stream and a gas deflector disposed adjacent the outlet toassist in the aeration of the gas prior to combustion, the bafflesurface of the deflector being inclined to the gas stream at between 40°and 50°.

The baffle surface may be inclined at between 44° and 46°, butpreferably is inclined to the gas stream at approximately 45°.

The deflector may be positioned such that the gas stream hits thedeflector at a region whose height is approximately two thirds of theheight of the deflector, taken from the base thereof.

This has been found to increase the stability of the flame produced bythe combustion of the gas.

Advantageously, the deflector is coated with or made from a ceramic orceramic fibre material, to reduce the amount of nitrogen oxides (NOx)produced by the combustion of the gas.

Specific and non-limiting embodiments of the aspects of the inventionwill now, be described, by way of example only, with reference to theaccompanying drawings, in which:

FIG. 1 shows a part cut-away perspective view of a gas burner accordingto the present invention;

FIG. 2 shows a side view of the gas burner in operation; and

FIG. 3 shows a schematic view of the gas burner.

Turning first to FIG. 1, a gas burner is shown generally at 10. The gasburner 10 has a burner bar 11 comprising a partly-sealed length oftubing 12 having a gas inlet (not shown) and a number of gas outlets 13,formed by drilled holes in the tubing 12. The gas outlets 13 are spacedso as to allow easy cross-lighting of gas streams issuing from the gasoutlets 13. Optionally, gas nozzles (not shown) may be fitted to the gasoutlets 13. Positioned above the burner bar 11 is an air guide plate 14,which is curved to correspond with the outer surface of the burner bar11 so as to direct air towards the gas outlets 13, as indicated by arrow17. The air guide plate 14 is fitted with a reinforcing lip 19 for addedstrength. Facing the gas outlets 13 is a deflector 15, mounted such thata front face (baffle surface) 23 of the deflector 15 is angled away fromthe gas outlets 13. In this example, the deflector is made from angleiron to prevent deformation of the deflector 15 at high temperatures,but other materials could also be used. In particular, the deflector 15may be made from, or coated with, a ceramic or ceramic fibre material tohelp reduce the amount of nitrogen oxides (NOx) produced. The deflector15 in this example has a generally triangular cross-section forstrength.

However, it will be understood by those skilled in the art that thedeflector 15 may have any suitable cross-section, or may be a singleflat plate. The horizontal distance between the burner bar 11 and thedeflector 15 is adjustable in accordance with the application for whichthe burner is to be used. The angle of the deflector relative to ahorizontal plane is also adjustable, such that the angle at which thegas streams hit the front face 23 of the deflector 15 is adjustable, asexplained in more detail below.

Turning next to FIG. 2, a gas burner 10 is shown in use. Gas is suppliedto the burner bar 11 through the gas inlet. Gas escapes from the burnerbar 11, in the form of jets/streams 21, through the gas outlets 13. Theescaping gas jets 21 hit the deflector 15 and experience turbulence 22,causing the gas to mix with atmospheric air surrounding the deflector15. For many feed gases such as propane, this mixing of the gas withairs combined with the air directed towards the escaping gas jets 21 bythe air guide plate 14 (indicated by arrows 17), and air from beneaththe burner bar 11 (indicated by arrows 18), ensures that sufficient airis present to allow complete or near-complete combustion of the gas whenit is ignited at the deflector 15. However, some gases, such as butane,require more air for complete or near-complete combustion. When suchgases are used, an appropriate amount of air may be added to the feedgas stream at the inlet or in the burner bar 11, to ensure complete, ornear-complete, combustion. In order to reduce problems caused by“feedback” of gas and/or combustion products, and to ensure that thenecessary turbulence is created, the air introduced into the feed gasstream must be at a pressure greater than that of the feed gas. As willbe understood by those skilled in the art, additional controls; whichare known per se, may be required to ensure the safety and correctoperation of such an arrangement. In either case, a fan-shaped flame 16,generally blue in colour, is produced at the deflector 15.

Turning lastly to FIG. 3, there is shown a schematic side view of aburner. Through testing, it has been found by the applicants that, for agiven size of burner bar, the horizontal distance between the burner bar11 and the deflector 15 (indicated by arrow 40) is dependent upon therequired heat output of the burner 10. For small heat outputs, a smalldistance 40 is required, whereas for larger heat outputs, a largerdistance 40 is required. It has, also been found by the applicants thatthe amount of aeration of the gas jets 21 issuing from the gas outlets13 is dependent upon the angle 41 at which the gas jets 21 hit thedeflector 15. For example, if the angle 41 is less than 44 degrees, lessturbulence 22 is created at the deflector 15, which results in lessaeration of the gas jets 21 and thus less complete combustion of the gas21: Increasing the angle 41 above 46 degrees also reduces the amount ofturbulence 22 created, again causing less complete combustion of thegas, as well as giving rise to a risk that the flame 16 will. ‘lift off’the deflector 15, moving away from a position at which optimum heatingoccurs. It has been found that the optimum, angle 41 is 45 degrees toensure correct aeration of the gas 21 and therefore complete ornear-complete combustion. It has also been found that, for maximumstability of the flame 16, the point at which the gas 21 hits thedeflector 15 should be approximately two-thirds of the height of thedeflector 15 from the base of the deflector 15, as shown (approximately)in FIG. 2.

In the drawings the gas ‘outlets ’13 are shown to emit gas in agenerally horizontal direction. It is to be understood that the presentinvention may equally be employed using gas outlets which emit gas in amore vertical direction, although for downward firing applications, itmay be necessary to extract the combustion products so that they do not,interfere with the combustion process.

When used in this specification and claims, the terms “comprises” and“comprising” and variations thereof mean that the specified features,steps or integers are included. The terms are not to be interpreted toexclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

1. A gas burner comprising a gas supply element having an outlet, and agas deflector disposed adjacent the outlet, the position of thedeflector, relative to the outlet, being adjustable so as to allow theextent of deflector-induced aeration to be altered.
 2. A gas burneraccording to claim 1 wherein the angle of the deflector, relative to theoutlet, is adjustable.
 3. A gas burner according to claim 1 wherein thespacing of the deflector, relative to the outlet, is adjustable.
 4. Agas burner according to claim 1, wherein the angle and spacing of thedeflector, relative to the outlet, are adjustable.
 5. A gas burneraccording to claim 1 wherein the supply element comprises a conduithaving a plurality of spaced outlets, the deflector being provided by abaffle surface adjacent the outlets, such that gas emitted therefrom isincident upon spaced regions of the baffle surface.
 6. A gas burneraccording to claim 5 wherein the conduit is a closed pipe, the pipebeing generally straight, with the baffle surface extending generallyparallel thereto.
 7. A gas burner according to claim 5 wherein thebaffle surface is generally flat.
 8. A gas burner according to claim 5,wherein the baffle surface is inclined relative to the gas streamsemitted through the outlets.
 9. A gas burner according to claim 5,wherein the baffle surface has a distal ridge.
 10. A gas burneraccording to claim 9 wherein the distance of the distal ridge from thegas steams is adjustable.
 11. A gas burner according to claim 1 furthercomprising an air guide to assist in the entrainment of air with gasemitted from the outlet.
 12. A gas burner according to claim 11 whereinthe air guide has guide surfaces disposed on at least two sides of theoutlet.
 13. A gas burner according to claim 12 wherein the outlet isgenerally horizontally-disposed, with the guide surfaces being disposedabove and below the outlet.
 14. A gas burner comprising a gas supplyelement having an outlet for the emission of a gas stream, and a gasdeflector disposed adjacent the outlet to assist in the aeration of thegas prior to combustion, the baffle surface of the deflector beinginclined to the gas stream at between 40° and 50°.
 15. A gas burneraccording to claim 14 wherein the baffle surface is inclined at between44° and 46°.
 16. A gas burner according to claim 14 wherein the bafflesurface is inclined to the gas stream at approximately 45°.
 17. A gasburner according to claim 1 wherein the deflector is positioned suchthat the gas stream hits the deflector at a region whose height isapproximately two thirds of the height of the deflector, taken from thebase thereof.
 18. (canceled)
 19. (canceled)